UV curable cellulose esters

ABSTRACT

The present invention relates to a modified cellulose ester containing unsaturated pendent groups which can be prepared by reacting a cellulose ester containing residual hydroxyl groups with, for example, maleic anhydride in acetic acid solvent with sodium acetate catalyst. The modified cellulose ester is not homopolymerizable but will copolymerize in the presence of vinyl crosslinking agents and a photoinitiator upon exposure to ultraviolet radiation. The modified cellulose ester is useful as a protective and/or decorative coating for wood, metal, plastics, paper, board, and other substrates, as well as an additive to printing inks, and as a nail polish. In addition, because of the propensity for the pendant carboxyl groups to form hydrophilic salts with amines, the modified cellulose esters can be formulated to be water-dispersible.

FIELD OF THE INVENTION

This invention belongs to the field of polymer chemistry. In particular,this invention relates to certain cellulose ester derivatives whichpossess groups capable of free radical addition reactions with ethylenicgroups on other compounds upon exposure to ultraviolet light in thepresence of an initiator, thermally, or when exposed to electron beamradiation.

BACKGROUND OF THE INVENTION

Cellulose esters are used extensively in lacquer coatings because theyare compatible with many resins and additives, they exhibit goodgap-filling properties, they dry quickly, they can be sanded or rubbedsoon after application, they exhibit low toxicity, and they form a veryaesthetically-pleasing coating on a variety of substrates. Such coatingscan be applied with reproducible results and can be repaired or evenremoved with the use of solvent. Such lack of solvent resistance is anadvantage for lacquer handling since equipment used to apply the lacquercan be readily cleaned and the coating can be repaired easily ifdamaged. However, good solvent and stain resistance of the appliedcoating also is highly desirable, particularly if the coating isintended to be protective in nature. Moreover, cellulose ester lacquercoatings tend to be rather soft and are easily scratched.

Thermoset coatings have excellent solvent resistance and hardnessproperties, but they also have serious disadvantages. Most are thermallycured or crosslinked and their use is thus limited to substrates whichare stable at the curing temperatures which can be as high as 230° C.Moisture-cured systems have been used to overcome the use of high curetemperatures but these have prolonged cure times and have humidityrequirements for such curing. The use of ultraviolet radiation totransform a photocrosslinkable thermoplastic coating into a thermosetcoating thus represents a potentially desirable improvement. Curing canoccur over a period of seconds to yield a hard, stain-resistant coating.In this manner, the advantages of both thermoplastic and thermosetpolymers can be maintained.

It is also highly desirable to limit the amount of solvent used to applysuch coatings due to environmental and work exposure issues. The use ofwater dispersible resins and resins dissolved in reactive solventsrepresent two potential solutions.

Attempts have been made to prepare cellulose-based resins that seek toprovide such desired coatings and methods of application; however, suchattempts have major deficiencies. For example, U.S. Pat. Nos. 4,112,182;4,490,516; 3,749,592; and 4,147,603 do not provide crosslinkable resinshaving the desired level of solvent resistance and hardness, nor do anyof these references teach the use of these resins in water dispersibleor reactive solvent coatings.

Photopolymerizable cellulose esters described in U.S. Pat. No. 4,565,857display a wide range of reactivities. For example, cellulose acetatepropionate grafted with 2-isocyanatoethyl methacrylate per mole ofanhydroglucose units has a short pot life in the presence of peroxidesor a photoinitiator such as Ciba Geigy's IRGACURE® 651 Photocuring Agent(2,2-dimethoxy-2-phenylacetophenone) and can gel unexpectedly.

Other cellulose esters such as cellulose acetate propionate grafted with0.9 moles of m-isopropyl-alpha, alpha-dimethylbenzyl isocyanate per moleof anhydroglucose units completely fail to crosslink when exposed to UVradiation in the presence of a photoinitiator.

U.S. Pat. No. 4,839,230 describes grafted cellulose esters prepared byreacting a hydroxy-functional cellulose ester with an acrylic basedcompound and m-isopropenyl-α,α-dimethylbenzylisocyanate.

U.S. Pat. Nos. 4,565,857 and 4,839,230 also require the use ofisocyanates for attachment of the ethylenically unsaturated moieties tothe polymer backbone. This requires the manufacturing process to bemoisture free, otherwise the isocyanate moiety reacts with water to formurea by-products which can cause deleterious effects by crystallizingout in the films made from the described resins.

SUMMARY OF THE INVENTION

The present invention provides modified cellulose esters capable of freeradical polymerization with other ethylenically unsaturated species whenexposed to ultraviolet light. In particular, the invention providescellulose esters which have been reacted with maleic anhydride toprovide maleic or fumeric pendant groups on such modified celluloseesters. The modified cellulose esters can be neutralized with a base toprovide a water-disperisble resin suitable for use in waterborne coatingcompositions. These modified cellulose esters are useful in formulationswith other ethylenically unsaturated species and can be cured uponexposure to ultraviolet light in the presence of a photoinitiator toform a hard coating.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an ethylenically unsaturated celluloseacetate ester containing carboxylic acid pendant groups attached to thepolymer backbone of the formula ##STR1## wherein:

R¹ is independently maleate, fumarate, or a mixture thereof;

R² and R³ are independently ##STR2## or a mixture thereof;

x is 0.1 to 2.5,

y is 0.1 to 2.0,

z is 0.1 to 2.5, and

n is 30-250, provided that the sum of x, y, and z is in the range of 0.3to 3.0.

It should be understood from the above structure that the groupdesignated "C₆ H₇ O₄ " denotes the residue of alternate halves of ananhydroglucose unit, i.e., a group of the formula ##STR3## wherein thevarious R groups are R¹, R², and R³ as shown above.

As used herein, the term "cellulose ester" means an unmodified celluloseester, and the term "modified cellulose ester" means the modifiedcellulose ester of the invention which is a cellulose ester having amaleate or fumarate ester pendant group. Such polymers can be renderedwater dispersible by reaction with amines.

In a further preferred aspect of the present invention, the modifiedcellulose esters of the present invention are blended with co-reactivecompounds or polymers which possess ethylenic unsaturation which iscapable of free radical addition reaction with the maleate or fumaratependant groups on the modified cellulose esters. Examples of suchpolymers include epoxy acrylates, urethane acrylates, polyesteracrylates, and vinyl acrylates.

The modified cellulose esters of the present invention can be preparedby reacting maleic anhydride and a cellulose ester in the presence of analkaline earth metal or ammonium salt of a lower alkyl monocarboxylicacid catalyst, and at least one saturated monocarboxylic acid having 2to 4 carbon atoms, wherein said cellulose ester has a degree ofsubstitution per anhydroglucose unit of residual hydroxyl groups ofabout 0.1 to 2.0, in the presence of a suitable solvent. The alkalinemetal, alkaline earth metal, or ammonium salt of the lower alkylmonocarboxylic acid can be added directly to the reaction mixture or canbe generated in situ. The reaction is generally conducted at atemperature of about 50° C. to 120° C., preferably about 70° C. to about85° C. The reaction time is about 1 to 12 hours. Such solvents wouldinclude lower alkyl monocarboxylic acids such as acetic, propionic,isobutyric, and butyric acid, and mixtures thereof. In such reactions,the solvent:cellulose ester ratio by weight varies from about 1:1 toabout 20:1, preferably about 2:1 to 5:1.

In the process for preparing the modified cellulose ester, it ispreferred that the cellulose ester starting material has a degree ofsubstitution (DS) per anhydroglucose unit of residual hydroxyl groups ofabout 0.3 to about 2.0.

The cellulose ester starting materials may be of the acetate,propionate, or butyrate type, or mixed esters thereof. The degree ofsubstitution per anhydroglucose unit of residual hydroxyl groups forthese cellulose esters is in the range of about 0.1 to about 2.0 withabout 0.3 to about 1.5 being the preferred range. Typical startingcellulose esters include, but are not limited to; CA 320, CA 398, CAB381, CAB 551, CAB 553, CAP 482, CAP 504, all commercially available fromEastman Chemical Company, Kingsport, Tenn. Such cellulose ester startingmaterials typically have a number average molecular weight of betweenabout 10,000 and about 75,000 daltons as determined by gel permeationchromatography using polystyrene standards.

The molar proportions of starting materials used in the manufacturingprocess of the present invention are those proportions sufficient toresult in the desired degree of substitution of the modified celluloseester to achieve the desired product.

Suitable solvents for preparing the modified cellulose ester of thepresent invention include, but are not limited to ketones, esters,aliphatic monocarboxylic acids, and chlorinated hydrocarbons. Specificexamples include, but are not limited to acetone, 2-butanone, ethylacetate, propyl acetate, chlorobenzene, methylene chloride, chloroform,acetic acid, and propionic acid. Reactions are typically carried out inabout 40 to about 90 wt % solvent solutions based upon the weight of thecellulose ester starting material.

Suitable catalysts useful for preparation of the modified celluloseesters in the present invention include, but are not limited to, aminessuch as triethylamine, tributylamine, diisopropylamine, and pyridine;alkali metal salts of aliphatic carboxylic such as sodium acetate,potassium acetate, calcium acetate, sodium propionate and potassiumpropionate; and alkali metal carbonate salts such as sodium carbonateand potassium carbonate. A typical catalyst concentration used is about25 to about 100 wt % based on the weight of the starting celluloseester.

In the synthesis processes of the present invention, the reaction isperformed under conditions such that the desired modified celluloseester is formed. Typically the reaction period is about 1 to about 12hours, preferably about 2 to about 5 hours. The temperature during thereaction is typically about 50° to about 120° C., preferably about 60°to about 80° C.

A preferred process of the present invention is summarized in thefollowing sequential steps:

1. An appropriate cellulose ester starting material is dissolved in asuitable solvent such as reagent grade acetic acid to obtain a solventsolution.

2. The reaction mixture is heated to 65° C.

3. Maleic anhydride is then added and agitated until dissolved.

4. Sodium acetate is added.

5. The reaction mixture is heated to 75° C. for three hours.

In the process of the invention for facilitating isolation of themodified cellulose ester, the non-solvent is a liquid in which themodified cellulose ester is not soluble. Such nonsolvents include butare not limited to water, isopropyl alcohol, hexane, heptane, andmixtures thereof. The amount of nonsolvent used in the process toprecipitate the modified cellulose ester is about 25 to about 100 wt %of nonsolvent based on the total weight of the reaction mixture. It ispreferred that such process includes the additional step of separatingthe precipitated modifier cellulose ester from unprecipitated reactionby-products. Unprecipitated by-products typically include maleic acid,sodium maleate, reaction catalyst, and mixtures thereof.

In a preferred process for isolating and facilitating isolating themodified cellulose ester, after Step 5, the following sequential stepsare followed:

6. The reaction mixture is cooled to 50° C. and drowned into water withrapid agitation to precipitate the modified cellulose ester.

7. The modified cellulose ester product is filtered and washed withwater to remove unprecipitated reaction by-products. Also, the drowning,filtering, and drying steps may be repeated to further purify thedesired product.

8. The water-wet modified cellulose ester is dried at 60° C. in a vacuumoven.

Thus, the present invention provides a process for preparing themodified cellulose esters of the invention, which comprises:

(a) dissolving cellulose acetate, cellulose acetate propionate, orcellulose acetate butyrate in a solvent of the formula ##STR4## whereinR⁴ is C₁ -C₃ alkyl to provide a solution; (b) heating said solution to atemperature of about 50° C. to 120° C.;

(c) treating said solution with maleic anhydride, and a catalystselected from the group consisting of an alkaline metal salt, alkalineearth salt, or ammonium salt; and

(b) continuing heating at a temperature of about 50° C. to 120° C..

As a further aspect of the invention, there is provided a method forisolating the modified cellulose ester of the present invention whereinsaid cellulose ester is in unprecipitated form and is in a mixture withreaction by-products and a suitable solvent. This isolation processcomprises contacting said mixture with an amount of nonsolventsufficient to precipitate the desired product. The amount of water usedto precipitate the product varies from about 1:4 (parts of water:partsof reaction mixture by weight) to about 5:1, preferably about 0.5:1 toabout 1.2:1. The resulting precipitate can be filtered or centrifugedand washed with water, preferably at a temperature of about 10° C. to90° C.

Alternatively, the modified cellulose esters of the present inventioncan be prepared by dissolving the cellulose ester in an organic solventdevoid of carboxylic acids and reacting it with maleic anhydride in thepresence of a proton acceptor. The reaction is heated and the productprecipitated by mixing a non-solvent with the reaction mixture. Theproduct is then isolated by filtration, washed with water, and dried. Inthis regard, suitable organic solvents include ketones such as acetone,2-butanone, 2-pentanone, cyclohexanone; esters such as methyl, ethyl,propyl, iso-propyl, isobutyl, and butyl esters of lower alkyl carboxylicacids; ethers such as diethyl and dibutyl ethers, dialkyl ethers ofglycols such as dimethyl, dipropyl, and dibutyl glycols of ethylene andpropylene glycols, tetrahydrofuran, and dioxane; dialkyl esters of loweralkyl monocarboxylic acids of ethylene and propylene glycols such asdiacetyl, dipropionyl, dibutyrl esters of ethylene and propyleneglycols; sulfoxides such as sulfolane, dimethyl sulfoxide and diethylsulfoxide; dialkylamides of formic, acetic, and propionic acids,N-methyl pyrrolidinone; and chlorinated hydrocarbons such as methylenechloride, chloroform, and chlorobenzene.

The solvent:cellulose ester ratio by weight is generally from about 1:1to about 20:1, preferably about 2:1 to about 5:1.

The proton acceptor can be, for example, a trialkyl amine such astrimethylamine, triethylamine, tripropylamine, tributylamine, or amixture thereof; alkyl substituted pyrrolidines and piperidines; dialkylanilines; pyridine and alkyl substituted pyridines; and inorganicalkaline and alkaline earth carbonates. Such proton acceptors arepreferably present in a proportion of about 0.1:1 to about 1:1 (protonacceptor:cellulose ester, by weight).

The temperature for the reaction is about 50° C. to 120° C., preferablyabout 70° C. to 85° C.. The reaction time is generally about 1 to 12hours. The product can be isolated by adding a reaction mixture-misciblenon solvent and isolated by filtration or centrifugation, followed bywashing with water, preferably at a temperature of about 10° C. to 90°C. and dried.

Thus, as a further aspect of the invention, there is provided a processfor preparing a cellulose acetate ester of the formula ##STR5##

wherein:

R¹ is independently maleate, fumarate, or a mixture thereof;

R² and R³ are independently ##STR6## mixture thereof;

x is 0.1 to 2.5,

y is 0.1 to 2.0,

z is 0.1 to 2.5, and

n is 30-250, provided that the sum of x, y, and z is in the range of 0.3to 3.0;

which comprises;

(a) dissolving cellulose acetate, cellulose acetate propionate, orcellulose acetate butyrate in an organic solvent free of carboxylicacids to provide a solution;

(b) heating said solution to a temperature of about 50° C. to 120° C.;

(c) treating said solution with maleic anhydride, in the presence of aproton acceptor.

In the modified cellulose ester of the present invention it is preferredthat x is about 0.1 to about 0.4, y is about 0.1 to 0.5, and z is 0.1 to2.5.

In the undispersed (i.e., solvent-borne) coating composition of thepresent invention the suitable solvent must be one in which the modifiedcellulose ester is soluble. Aliphatic hydrocarbons are generally notsuitable for this purpose. Typical examples of suitable solventsinclude, but are not limited to ketones, esters, chlorinatedhydrocarbons, aqueous buffer solutions, and mixtures thereof. Specificexamples include, but are not limited to acetone, 2-butanone,2-pentanone, ethyl acetate, propyl acetate, butyl acetate, methylalcohol, ethyl alcohol, ethylene glycol monoethyl ether, and mixturesthereof. Also, further suitable solvents can be of the ethylenicallyunsaturated type that, in addition to dissolving the modified celluloseester, can crosslink with the cellulose upon exposure to UV radiation inthe presence of a photoinitiator. Specific examples include, but are notlimited to, ethyl(meth)acrylate, methyl(meth)acrylate,hydroxyethyl(meth)acrylate, diethylene glycol diacrylate,trimethylolpropane triacrylate, 1,6 hexanediol di(meth)acrylate,neopentyl glycol di(meth)acrylate, and mixtures thereof.

The amount of suitable solvent in the non-dispersed water-based coatingcomposition of the present invention is that amount sufficient tosolubilize the modified cellulose ester. Typically, this amount is about60 to about 90 weight % of total coating composition, preferably about65 to about 75 weight %. Mixtures of solvents can be used in thecoatings (and processes) of the present invention.

In the water-dispersed coating composition of the present invention thesuitable co-solvent must be one that is water miscible and that willsolubilize the modified cellulose ester. Typical examples include butare not limited to acetone, 2-butanone, methanol, ethanol, ethyleneglycol monoethyl ether, ethylene glycol monopropyl ether, and ethyleneglycol monobutyl ether. Typical examples of ethylenically unsaturatedsolvents include, but are not limited to, 2-ethoxyethyl(meth)acrylate,polyethylene glycol dimethacrylate, polypropylene glycol mono(meth)acrylate, and mixtures thereof.

Dispersion of the modified cellulose ester of the present invention inwater requires about 25 to about 100% neutralization of the pendantcarboxylate groups with an aliphatic amine. Typical aliphatic aminesinclude but are not limited to piperidine, 4-ethylmorpholine,diethanolamine, triethanolamine, ethanolamine, tributylamine,dibutylamine, and ammonia.

The amount of suitable aqueous solvent in the dispersed coatingcomposition of the present invention is 50 to about 90 wt %, preferablyabout 75 to about 90 wt % of the total coating composition.

The coating compositions of the present invention optionally contain aphotoinitiator. The amount of photoinitiator is typically about 2 toabout 7 wt % based on the weight of the non-volatile content of thecoating composition; preferably about 3 to about 5 wt %. Suitablephotoinitiators include, but are not limited to, acetophenone/ andbenzophenone/tertiary amine combinations, organic peroxides, benzoin andits ethers, benzil and benzil ketals. A preferred photoinitiator isIRIGACURE® 651 Photocuring Agent (2,2-dimethoxy-2-phenylacetophenone),available from Ciba-Geigy. If a UV curable composition is desired, aphotoinitiator must be present. In the case of electron beam curing, thephotoinitiator may be omitted. Further details regarding suchphotoinitiators and curing procedures can be found in U.S. Pat. No.5,109,097, incorporated herein by reference.

The coating composition may contain other formulation additives whichcontribute to the non-volatile content of the composition. Suchadditives include, for example, leveling agents, antifoamants, and thelike. Such additives may be present in an amount from about 0.1 to about5 wt % of total coating composition, preferably about 0.1 to about 1.0wt %.

As a further aspect of the present invention there is provided a curablecomposition as described above, further comprising one or more leveling,rheology, and flow control agents such as silicones, fluorocarbons orcellulosics; flatting agents; pigment wetting and dispersing agents;surfactants; ultraviolet (UV) absorbers; UV light stabilizers; tintingpigments; defoaming and antifoaming agents; anti-settling, anti-sag andbodying agents; anti-skinning agents; anti-flooding and anti-floatingagents; fungicides and mildewcides; corrosion inhibitors; thickeningagents; or coalescing agents.

Specific examples of such additives can be found in Raw Materials Index,published by the National Paint & Coatings Association, 1500 RhodeIsland Avenue, N.W., Washington, D.C. 20005.

Examples of flatting agents include synthetic silica, available from theDavison Chemical Division of W. R. Grace & Company under the trademarkSYLOID®; polypropylene, available from Hercules Inc., under thetrademark HERCOFLAT®; synthetic silicate, available from J. M HuberCorporation under the trademark ZEOLEX®.

Examples of dispersing agents and surfactants include sodiumbis(tridecyl) sulfosuccinnate, di(2-ethyl hexyl) sodium sulfosuccinnate,sodium dihexylsulfosuccinnate, sodium dicyclohexyl sulfosuccinnate,diamyl sodium sulfosuccinnate, sodium diisobutyl sulfosuccinate,disodium iso-decyl sulfosuccinnate, disodium ethoxylated alcohol halfester of sulfosuccinnic acid, disodium alkyl amido polyethoxysulfosuccinnate, tetrasodium N-(1,2-dicarboxy-ethyl)-N-oxtadecylsulfosuccinnamate, disodium N-octasulfosuccinnamate, sulfatedethoxylated nonylphenol, 2-amino-2-methyl-1-propanol, and the like.

Examples of viscosity, suspension, and flow control agents includepolyaminoamide phosphate, high molecular weight carboxylic acid salts ofpolyamine amides, and alkyl amine salt of an unsaturated fatty acid, allavailable from BYK Chemie U.S.A. under the trademark ANTI TERRA®.Further examples include polysiloxane copolymers, polyacrylate solution,cellulose esters, hydroxyethyl cellulose, hydrophobically-modifiedhydroxyethyl cellulose, hydroxypropyl cellulose, polyamide wax,polyolefin wax, carboxymethyl cellulose, ammonium polyacrylate, sodiumpolyacrylate, and polyethylene oxide.

Several proprietary antifoaming agents are commercially available, forexample, under the trademark BRUBREAK of Buckman Laboratories Inc.,under the BYK® trademark of BYK Chemie, U.S.A., under the FOAMASTER® andNOPCO® trademarks of Henkel Corp./Coating Chemicals, under the DREWPLUS®trademark of the Drew Industrial Division of Ashland Chemical Company,under the TROYSOL® and TROYKYD® trademarks of Troy Chemical Corporation,and under the SAG® trademark of Union Carbide Corporation.

Examples of fungicides, mildewcides, and biocides include4,4-dimethyloxazolidine, 3,4,4-trimethyloxazolidine, modified bariummetaborate, potassium N-hydroxy-methyl-N-methyldithiocarbamate,2-(thiocyanomethylthio) benzothiazole, potassium dimethyldithiocarbamate, adamantane, N-(trichloromethylthio) phthalimide,2,4,5,6-tetrachloroisophthalonitrile, orthophenyl phenol,2,4,5-trichlorophenol, dehydroacetic acid, copper naphthenate, copperoctoate, organic arsenic, tributyl tin oxide, zinc naphthenate, andcopper 8-quinolinate.

Examples of U.V. absorbers and U.V. light stabilizers includesubstituted benzophenone, substituted benzotriazole, hindered amine, andhindered benzoate, available from American Cyanamide Company under thetradename Cyasorb UV, and available from Ciba Geigy under the trademarkTINUVIN, and diethyl-3-acetyl-4-hydroxy-benzyl-phosphonate,4-dodecyloxy-2-hydroxy benzophenone, and resorcinol monobenzoate.

Such paint or coating additives as described above form a relativelyminor proportion of the enamel composition, preferably about 0.05 weight% to about 5.00 weight %.

To prepare the coated articles of the present invention, the modifiedcellulose ester of the present invention is applied to a substrate andthen is cured (i.e., polymerized and crosslinked), in the presence ofIRGACURE® 651 benzil ketal, IRGACURE® 184 benzil, or DAROCURE® 1173benzil, by an amount of ultraviolet radiation sufficient to effect thedesired degree of curing. The substrate can be, for example, wood;plastic; metal such as aluminum or steel; cardboard; glass; celluloseacetate butyrate sheeting; and various blends containing, for example,polypropylene, polycarbonate, polyesters such as polyethyleneterephthalate, acrylic sheeting, as well as other solid substrates.

The coating composition of the present invention is preferably furthercomprised of auxiliary polymerizable monomers and/or oligomers such as,but not limited to, vinyl acetate, N-vinyl pyrrolidonemethyl(meth)acrylate, butyl(meth)acrylate, 2-hydroxyethyl(meth)acrylate, neopentylglycol di(meth)acrylate, triethyleneglycoldi(meth)acrylate, trimethylolpropane triacrylate, (meth)acrylatedurethanes such as EBECRYL® 220, SARTOMER® CN 964 and CN 965;(meth)acrylated epoxies such as SARTOMER® CN 104; and (meth)acrylatedpolyesters and polyethers.

The curing of the modified cellulose esters of the present invention canbe carried out in the liquid or solid state (i.e., as a dry film).

Depending upon the thickness of the coating (film), product formulation,photoinitiator type, radiation flux, and source of radiation, exposuretimes to ultraviolet radiation of about 0.5 to about 10 seconds aretypically required for curing.

The coating on the coated article of the present invention typically hasa solvent resistance of at least 100 double rubs using ASTM ProcedureD-3732; preferably a solvent resistance of at least about 200 doublerubs. Such coating also typically has a pencil hardness of greater thanor equal to F using ASTM Procedure D-3363; preferably a pencil hardnessof greater than or equal to H.

The modified cellulose esters are also useful in fingernail polishcompositions.

The general formulation for UV-curable fingernail polishes containingmodified cellulose esters of the present invention is as follows:

5-50% modified cellulose ester as the major film former

10-90% copolymerizable monomer

0-10% modifying resin

0-25% plasticizer

0-5% pigment

2-7% photoinitiator

0-90% solvents

Typical copolymerizable monomers are (meth)acrylic acid, crotonic acid,maleic acid, fumaric, itaconic acid and their anhydrides, cyanoacrylic;esters of (meth)acrylic acid such as allyl, methyl, ethyl, n-propyl,isopropyl, butyl, tetrahydrofurfuryl, cyclohexyl, isobornyl, n-hexyl,n-octyl, isooctyl, 2-ethylhexyl, lauryl, stearyl, benzyl, andsubstituted phenoxyl, behenyl; di(meth)acrylate esters of ethylene andpropylene glycols, 1,3-butylene glycol, 1,4-butanediol, diethylene anddipropylene glycols, triethylene and tripropylene glycols,1,6-hexanediol, neopentyl glycol, polyethylene glycol, and polypropyleneglycol, ethoxylated bisphenol A, propoxylated neopentyl glycol;tri(meth)acrylate esters of tris-(2-hydroxyethyl)isocyanurate,trimethylolpropane, pentaerythritol, glycerol, ethoxylated andpropoxylated glycerol; tetra(meth)acrylate esters of pentaerythritol;acrylonitrile, vinyl acetate, vinyl toluene, styrene,N-vinylpyrrolidinone, and alpha-methylstyrene.

Typical modifying resins include homopolymers and copolymers of(meth)acrylic acid; alkyl esters of (meth)acrylic acid such as allyl,methyl, ethyl, n-propyl, isopropyl, butyl, tetrahydrofurfuryl,cyclohexyl, isobornyl, n-hexyl, n-octyl, isooctyl, 2-ethylhexyl, lauryl,stearyl, benzyl; (meth)acrylated urethane, epoxy, and polyester resins,silicone acrylates.

Typical (meth)acrylated epoxy resins would be ACTILANE 7220 TP, ACTILANE72, and ACTOCRYL 10020 A from Anchor Chemical (UK); CRODAMER UVE seriesfrom Croda; CRAYNOR CN104 and 114 from Cray Valley; DEREKANE 200 fromDow Europe S.A.; EBECRYL 200, 220, and 3700 from Radcure Specialties;and PHOTOMER 3015 and 3016 from Henkel.

Typical (meth)acrylated urethanes are ACTILANE 20, 23, and 27 fromAnchor Chemical (UK); CRAYNOR CN 934, 946, 960, and 965 from CrayValley; Daicel SR 6010, 6012, 6022, and 6023 from Daicel ChemicalIndustries; EBECRYL 230, 270, 1290, 5129, and 8804 by RadcureSpecialties; PHOTOMER 6008, 6010, 6338, and 6264 by Henkel.

Typical (meth)acrylated polyester resins would be EBECRYL 657, 810, 830,and 1657 from Radcure Specialties; LAROMER LR 8799 and 8800 by BASF; andPHOTOMER 5007, 5018, and 5029 from Henkel.

Typical silicone (meth)acrylates include EBECRYL 350 and 1360 fromRadcure Specialties; PHOTOMER 7020 from Henkel; TEGO 704, 705, 725, and726 from Goldschmidt AG; and WACKER F-737 by Wacker Silicones.

Typical plasticizers include alkyl esters of phthalic acid such asdimethyl phthalate, diethyl phthalate, dipropyl phthalate, dubutylphthalate, and dioctyl phthalate; citrate esters such as triethylcitrate and tributyl citrate; triacetin and tripropionin; and glycerolmonoesters such as MYVEROL 18-04, 18-07, 18-92 and 18-99 from EastmanChemical Company.

Typical solvents include lower molecular weight alcohols such asethanol, propanol, isopropyl alcohol, butanol, pentanol, hexanol, and2-ethylhexanol; glycols such as ethylene and propylene glycols; ketonessuch as acetone, 2-butanone, and 2-pentanone; esters such as methyl andethyl acetate, isopropyl acetate, butyl and isobutyl acetate, ethyleneglycol diacetate, propylene glycol diacetate.

Typical photoinitiators include benzoin and benzoin ethers such asESACURE BO, EB1, EB3, and EB4 from Fratelli Lamberti; VICURE 10 and 30from Stauffer; benzilketals such as IRGACURE 651 from Ciba Geigy,Uvatone 8302 by Upjohn; alpha, alpha-dialkoxyacetophenone derivativessuch as DEAP and UVATONE 8301 from Upjohn; alpha-hydroxyalkylphenonessuch as IRGACURE 184 from Ciba Geigy; DAROCUR 116, 1173, and 2959 byMerck; mixtures of benzophenone and tertiary amines.

A specific formulation for a UV-curable fingernail polish based on amodified cellulose ester of the present invention is the following:

25 parts modified cellulose ester (major film former)

12 parts ethyl acetate

24 parts butyl acetate

8 parts acrylated urethane resin (EBECRYL 220 from Radcure Industries)

22 parts tripropyleneglycol diacrylate

5 parts N-vinylpyrrolidone

4 parts IRGACURE 651 photoinitiator (Ciba Geigy)

Experimental Section EXAMPLE 1

Preparation of CAP 504 cellulose acetate propionate grafted with TMI®isocyanate and methacrylate groups

A solution is made consisting of 100 g of dry CAP 504-0.2 (availablefrom Eastman Chemical Company--cellulose acetatepropionate--approximately 42.5 weight percent propionyl content, 0.6weight percent acetyl content, and 5.0 weight percent hydroxyl content)and 500 g of urethane-grade propyl acetate. The solution is brought toreflux and approximately 100 g of propyl acetate is distilled out toazeotropically dry the cellulose ester. The solution is cooled to 50° to60° C. and 0.5 g of dibutyltin dilaurate catalyst and 33 g of TMI®(meta-isopropenyl-2,2'-dimethyl benzyl isocyanate, availablecommercially from Cytec) are added. The reaction mixture is refluxeduntil the --NCO absorption in the infrared spectrum of the reactionmixture is no longer discernible from the baseline. The reaction mixtureis cooled to 30° C. The following are added: 26 grams of triethylamine,0.5 g hydroquinone monomethyl ether, and 40 g of methacrylic anhydride.The reaction mixture is refluxed for 6 hours, cooled to 30° C., anddrowned into 1 liter of hexane with high speed agitation. The celluloseester is filtered and dried at 60° C.

The analysis of the cellulose ester product by nuclear magneticresonance showed the degree of substitution per anhydroglucose forpropionate, TMI moiety, and methacrylate to be 2.0, 0.6 and 0.1,respectively.

EXAMPLE 2

Preparation of CAP 504-maleate (Sample 4)

In a 5-gallon sigma blade mixture are placed 7300 g reagent grade aceticacid and 2500 g of CAP 504-0.2, commercially available from EastmanChemical Company, Kingsport, Tenn. The reaction mixture is heated to 65°C. and agitated until all the cellulose ester dissolves. Then 1250 g ofmaleic anhydride is added and agitated at 65° C. until a clear solutionis obtained, after which 1250 g of anhydrous sodium acetate is added.The reaction mixture is heated at 75° C. for three hours and then cooledto 50° C., where upon it is drowned into 9000 g of water with high speedagitation to precipitate the modified cellulose ester product. Theprecipitated cellulose ester is collected by filtration and then washedwith 15,000 g of water. The water-wet modified cellulose ester productis then dried in a vacuum oven at 60° C. to a moisture content of lessthan 2%. Analysis by nuclear magnetic resonance showed the degree ofsubstitution per anhydroglucose unit for acetate, propionate and maleateto be 0.40, 2.09 and 0.39, respectively.

EXAMPLE 3

Preparation of CAB 553-0.4 (celluose acetate butyrate) maleate (Sample6)

In a 5-gallon sigma blade mixture are placed 7300 g reagent grade aceticacid and 2500 g of CAB 553-0.4, commercially available from EastmanChemical Company, Kingsport, Tenn. (cellulose acetate butyrate having abutyryl content of 46 weight percent, an acetyl content of 2 weightpercent, and a hydroxyl content of 4.8 weight percent). The reactionmixture is heated to 65° C. and agitated until all the cellulose esterdissolves. Then 1250 g of maleic anhydride is added and agitated at 65°C. until a clear solution is obtained, after which 1250 g of anhydroussodium acetate is added. The reaction mixture is heated at 75° C. forthree hours and then cooled to 50° C., where upon it is drowned into9000 g of water with high speed agitation to precipitate the modifiedcellulose ester product. The precipitated cellulose ester product iscollected by filtration and then washed with 15,000 g of water. Thewater-wet modified cellulose ester is then dried in a vacuum oven at 60°C. to a moisture content of less than 2%. Analysis by nuclear magneticresonance showed the degree of substitution (DS) per anhydroglucose unitfor acetate, butyrate, and maleate to be 0.15, 2.1, and 0.41,respectively.

In similar fashion additional samples of modified cellulose esters witha variety of DS of substituents were prepared and are given in the Table1 below:

                  TABLE 1                                                         ______________________________________                                        Cellulose Ester Maleates                                                      Sample 1        2        3     4     5     6                                  ______________________________________                                        Acetate                                                                              1.82 DS  0.22     0.22  0.40  0.20  0.15                               Propionate                                                                           --       2.20     2.10  2.09  2.05  --                                 Butyrate                                                                             --       --       --    --    --    2.0                                Maleate                                                                              0.32     0.0.10   0.25  0.39  0.46  0.41                               ______________________________________                                    

Coating Compositions of Modified Cellulose Ester Samples

Solutions of modified cellulose esters prepared as describedhereinbefore (Samples 1-6 and as in Example 1) were dissolved in butylacetate with a concentration of 20% by weight of modified celluloseester containing 5% by weight of photoinitiator (IRGACURE® 651 by CibaGeigy) and 10% by weight of EBECRYL® 220, an hexacrylated urethaneoligomer as a crosslinking agent.

Coating of Substrates

Samples 1-6 and the modified cellulose ester prepared in Example 1 wereused to coat a variety of substrates such as glass, wood, metal, andplastics. For each type, the coating operation was the same. Thesubstrate was coated with the above formulation using a knife blade. Thewet film thickness was about 10 mil. The solvent was evaporated to givea clear non-tacky film with a thickness of approximately 1 mil. Prior toexposure to UV radiation, each film was readily soluble in organicsolvents.

Film Curing

The dried film was exposed to UV radiation from a 200 watt per inchmedium pressure mercury vapor lamp housed in an American UltravioletCompany instrument using a belt speed of 25 ft. per minute. Two to fivepasses under the lamp resulted in a crosslinked coating with maximumhardness and solvent resistance.

Coating Evaporations

Pencil hardness (ASTM D3363), solvent resistance by the methyl ethylketone double-rub test, and solubility in acetone were measured for eachfilm before and after exposure to UV radiation. Data for control resinsare also included.

The pencil hardness scale is in order of increasing hardness:

5B 4B 3B 2B B HB F H 2H 3H 4H 5H

The methyl ethyl ketone (MFK) double rub test is carried out bysaturating a piece of cheesecloth with methyl ethyl ketone, and withmoderate pressure, rubbing the coating back and forth. The number ofdouble rubs is counted until the coating is removed. This test is inaccordance with ASTM Procedure D-3732.

The acetone solubility test is carried out by immersing a dry,pre-weighed sample of the film in acetone for 48 hours at 25° C. Thefilm is removed, dried for 16 hours at 60° C. in a forced-air oven, andreweighed. The weight percent of the insoluble film remaining iscalculated from the data.

    ______________________________________                                        COATING EVALUATIONS                                                                             Pencil Hardness MEK                                         Resin Description Rubs Acetone Insolubles                                     ______________________________________                                        Before Irradiation                                                            CA 320S (Control).sup.1                                                                         F       <10      Dissolved                                  CAP 504 (Control).sup.1                                                                         HB      <10      Dissolved                                  CAB 553 (Control).sup.1                                                                         2B      <10      Dissolved                                  CAP-TMI-MA (Ex. 1)                                                                              F       <10      Dissolved                                  CA Mal (0.32 DS) (Sample 1)                                                                     F       <10      Dissolved                                  CAP Mal (0.10 DS) (Sample 2)                                                                    F       <10      Dissolved                                  CAP Mal (0.25 DS) (Sample 3)                                                                    F       <10      Dissolved                                  CAP Mal (0.39 DS) (Sample 4)                                                                    F       <10      Dissolved                                  CAP Mal (0.46 DS) (Sample 5)                                                                    F       <10      Dissolved                                  CAB Mal (0.41 DS) (Sample 6)                                                                    HB      <10      Dissolved                                  After Irradiation                                                             CA 320S (Control).sup.1                                                                         F       <10      Dissolved                                  CAP 504 (Control).sup.1                                                                         HB      <10      Dissolved                                  CAB 553 (Control).sup.1                                                                         2B      <10      Dissolved                                  CAP-TMI-MA (Ex. 1)                                                                              H       <200     9096                                       CA Mal (0.32 DS) (Sample 1)                                                                     H/2H    <200     9496                                       CAP Mal (0.10 DS) (Sample 2)                                                                    F       <98      4296                                       CAP Mal (0.25 DS) (Sample 3)                                                                    H       <200     9096                                       CAP Mal (0.39 DS) (Sample 4)                                                                    H/2H    <200     9496                                       CAP Mal (0.46 DS) (Sample 5)                                                                    H       <200     9196                                       CAB Mal (0.41 DS) (Sample 6)                                                                    HF      <200     9296                                       ______________________________________                                         .sup.1 Not formulated                                                    

EXAMPLE 4

Dispersion of Modified Cellulose Ester (Sample 3) in Water

Into a container with an agitator are placed 15 g of CAP 504-0.2 maleate(0.25 DS maleate, 2.10 DS propionate, 0.25 DS acetate, with acid no. of45 mg KOH/g of polymer) and 30 g of ethylene glycol monobutyl ether. Thecontents are agitated until a clear solution is obtained and then 50% ofthe carboxyl groups are neutralized by adding 0.37 g of ethanolamine.After agitation for 5 minutes, 55 g of water is slowly added withagitation to generate a dispersion suitable for coating applications.

The formula below is useful for calculating the amount of amine to addfor neutralization to any degree of the carboxylic acid pendent groups.##EQU1##

EXAMPLE 4

Attempted dispersion of CAP 504-0.2 grafted with TMI® and methacrylategroups

Into a container with an agitator are placed 15 g of CAP 504-0.2 graftedwith TMI® and methacrylate groups prepared in Example 1 above and 30 gof ethylene glycol monobutyl ether. The mixture is stirred until a clearsolution is obtained, whereupon 0.37 g of ethanolamine are addedfollowed by 55 g of water. Upon addition of water the modified celluloseester precipitates and does not form a dispersion suitable for coatingapplications.

EXAMPLE 5

Formulation and use of modified cellulose ester as a protective woodcoating

Modified cellulose ester (Sample 3) was used in the followingformulations:

    ______________________________________                                        Component                 Parts by Wt.                                        ______________________________________                                        Modified cellulose ester (Sample 3)                                                                     16.4                                                Methyl amyl ketone        32.6                                                Methyl propyl ketone      15.5                                                TECSOL ® C 95 (ethyl alcohol, available from Eastman                                                28.2                                                Chemical Company)                                                             EBECRYL ® 6700        3.6                                                 (aromatic urethane diacrylate diluted with 15% of 1,6-                        hexanediol diacrylate--available from Radcure                                 Specialties)                                                                  EBECRYL ® 220         2.7                                                 (a multifunctional aromatic urethane acrylate containing                      and acrylated polyol diluent)                                                 IRGACURE ® 651        1.0                                                 ______________________________________                                    

The Brookfield viscosity at 25° C. was 79 cP.

The % solids content was 23.7%.

Application to and Curing of Wood Panels

Pine wood panels were first coated with a CAB/acrylic sealer, dried, andsanded with 32-grit sandpaper. Two coats of the above formulation werespray-applied and allowed to dry for 30 minutes. The panels were exposedin three passes to UV radiation from two 200 watt per inch mediumpressure mercury vapor lamps housed in an American Ultraviolet Companyinstrument using a belt speed of 20 ft. per minutes.

Evaluation of Cured Coating on Wood Panels

The following properties were measured using standard test procedures:

    ______________________________________                                        Property     Value          ASTM Method                                       ______________________________________                                        Print Resistance                                                                           5 lb/ln.sup.2 @ 50° C.                                                                D 2091-87                                         Hardness     16.0 Knoops    D 1474                                            Cold-check Resistance                                                                      21 cycles passed                                                                             D 12-11-87                                        Acetone Double Rubs                                                                        >200 rubs      D 3732                                            Stain Resistance                                                                           Results given below:                                                                         D 3023-88                                         ______________________________________                                        Staining Agent    Result                                                      ______________________________________                                        Ammonia           NS                                                          Bourbon           NS                                                          Hydrochloric acid, 2%                                                                           NS                                                          KOH, 10%          S                                                           Mustard           NS                                                          Red wine          NS                                                          Shoe Polish       NS                                                          Isopropyl alcohol, 70%                                                                          NS                                                          Pine oil cleaner  NS                                                          Nail polish remover                                                                             NS                                                          Iodine            NS                                                          ______________________________________                                    

EXAMPLE 6

Use of Modified Cellulose Ester in "100% Solids" UV-Curable CoatingFormulation

Sample 3 was used in the following formulation to demonstrate itsefficacy in "solventless" UV-cure formulations:

    ______________________________________                                        Component            Parts by Wt.                                             ______________________________________                                        Modified cellulose ester (Sample 3)                                                                8                                                        Roskydal ® 300 (Bayer)                                                                         43                                                       1,6 Hexanediol diacrylate                                                                          28                                                       2-Hydroxyethyl methacrylate                                                                        9                                                        EBECRYL ® 220    7                                                        IRGACURE ® 184 (Ciba Geigy)                                                                    5                                                        ______________________________________                                    

We claim:
 1. An ethylenically unsaturated cellulose acetate ester of theformula ##STR7## wherein: R¹ is independently maleate, fumarate, or amixture thereof;R² and R³ are independently ##STR8## or a mixturethereof; x is 0.1 to 2.5, y is 0.1 to 2.0, z is 0.1 to 2.5, and n is30-250, provided that the sum of x, y, and z is in the range of 0.3 to3.0.
 2. The cellulose acetate ester of claim 1 wherein x is 0.1 to 0.4,y is 0.1 to 0.5, and z is 0.1 to 2.5.
 3. The cellulose acetate ester ofclaim 1 wherein R¹ is maleate.
 4. The cellulose acetate ester of claim1, wherein R¹ is fumarate.